Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 13 Feb 2019 15:29:12 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To:     xiang xiao <xiaoxiang781216@gmail.com>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        linux-kernel@vger.kernel.org, Xiang Xiao <xiaoxiang@xiaomi.com>
Subject: Re: [PATCH] printk: add KERN_NOTIME to skip the timestamp
Message-ID: <20190213062912.GA23233@jagdpanzerIV>
References: <1549995065-27597-1-git-send-email-xiaoxiang@xiaomi.com>
 <20190212144606.4b7cf0f8@gandalf.local.home>
 <CAH2Cfb-Zd9TKgs52ROVGYg6F_hiN2ieWKwYPkxpVV8St+zwa2A@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAH2Cfb-Zd9TKgs52ROVGYg6F_hiN2ieWKwYPkxpVV8St+zwa2A@mail.gmail.com>
User-Agent: Mutt/1.11.3 (2019-02-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On (02/13/19 14:19), xiang xiao wrote:
> Here is my case:
> 1.A small MCU(Cortex M4) in SoC run RTOS
> 2.RTOS append timestamp to log for the accurate timing
> 3.RTOS send log to Linux kernel when buffer exceed the threshold
> 4.Kernel call printk to dump the received buffer
> So I want that printk skip the timestamp here.
> 
> > If anything, I would probably prefer that we export whether
> > time is being printed, and have the caller not print time if printk is
> > doing it already, than to add the complexity into printk itself.
> 
> Actually, the timestamp of our initial implementation like your
> suggestion come from printk,

cat /sys/module/printk/parameters/time ?

Y - we add time prefix
N - we don't add time prefix

	-ss